An Acousto-Optic Memory Correlator

N. J. Berg; B. J. Udelson; J. N. Lee

doi:10.1117/12.955814

13 December 1977 An Acousto-Optic Memory Correlator

N. J. Berg, B. J. Udelson, J. N. Lee

Proceedings Volume 0123, Optical Storage Materials and Methods; (1977) https://doi.org/10.1117/12.955814
Event: 21st Annual Technical Symposium, 1977, San Diego, United States

Abstract

A new photorefractive effect, resulting from the interaction of high-intensity, short-duration laser pulses with propagating acoustic waves, has been found in LiNbO₃. The acoustic wave pattern is stored as changes in the index of refraction (δn). The δn is proportional to the rf amplitude, and increases sublinearly with the number of laser pulses and as the 1.3 power of the incident laser energy density. The decay time varies from a few hours, when only green illumination (530 nm) is used, to several weeks when combined green and infrared illumination (1060 nm) are used. The On can be erased by exposure to ultraviolet radiation or by annealing at 250°C. This acousto-photorefractive effect has been utilized to construct an acousto-optic memory correlator wherein both the stored On and the On produced by a "live" propagating acoustic wave simultaneously modulate a low-power cw laser beam. The resultant detected signal is proportional to the correlation integral. The memory correlator operated at a center frequency of 10 MHz with a 1-MHz bandwidth. A large variety of complex signals, such as chirps and Barker codes, was stored and subsequently correlated. The stored signal strength is about 30 dB below that of the original live signal. Successful correlation with a live signal was achieved several weeks after storage.

Citation Download Citation

N. J. Berg, B. J. Udelson, and J. N. Lee "An Acousto-Optic Memory Correlator", Proc. SPIE 0123, Optical Storage Materials and Methods, (13 December 1977); https://doi.org/10.1117/12.955814

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